The present application relates to an intaglio printing plate, a production method for an intaglio printing plate, a production method for an electronic substrate, and a production method for a display device. More particularly, the present application relates to an intaglio printing plate for use in reverse printing, a production method for the intaglio printing plate, and a production method for an electronic substrate and a production method for a display device using an intaglio printing plate obtained by the production method.
In recent years, application of reverse printing to formation of a conductive pattern has been examined in production of electronic substrates, such as driving substrates (so-called back planes) for display devices, in order to achieve a lower cost and a finer pattern.
A conductive pattern is formed by reverse printing as follows:
First, an intaglio printing plate 201 is formed, as shown in FIG. 10A. The intaglio printing plate 201 is provided with depressions 201a corresponding to a conductive pattern to be formed. Further, a film of a conductive ink 205 is formed on a releasable surface of a blanket 203. Next, as shown in FIG. 10B, a surface of the blanket 203 on which the conductive ink 205 is provided is pressed into tight contact with a surface of the intaglio printing plate 201 on which the depressions 201a are provided. Then, as shown in FIG. 10C, the conductive ink 205 is transferred onto the contact surface of the intaglio printing plate 201 by peeling the blanket 203 off the intaglio printing plate 201, so that a printing plate 203a in which the conductive ink 205 partly remains as an ink pattern 205a on the releasable surface of the blanket 203 is obtained.
Next, as shown in FIG. 10D, the surface of the printing plate 203a provided with the ink pattern 205a is brought into tight contact with a substrate 207 for a display device. Subsequently, by peeling the printing plate 203a (blanket 203) off the substrate 207, as shown in FIG. 10E, the ink pattern 205a is formed on the substrate 207 by pattern transfer.
In such reverse printing, if the depressions 201a of the intaglio printing plate 201 have large apertures, as shown in FIG. 10B, the blanket 203 in tight contact with the intaglio printing plate 201 deflects and touches the bottoms of the depressions 201a. Consequently, when the blanket 203 is peeled off the intaglio printing plate 201, as shown in FIG. 10C, the conductive ink 205 is also transferred onto the bottoms of the depressions 201a, and lost portions A are formed in the ink pattern 205a left on the blanket 203. This causes printing failure. If the depth of the depressions 201a is increased to prevent this problem, pattern collapse occurs at fine depressions 201a. 
Accordingly, Japanese Unexamined Patent Application Publication No. 2007-160769 proposes a structure in which a plurality of projections are provided in depressions having large apertures. This publication says that pattern loss of a conductive pattern (ink pattern) can be made negligibly small by sufficiently reducing the area ratio of the projections to the depressions.
Japanese Unexamined Patent Application Publication No. 2006-231827 discloses another method in which the depth of grooves in an intaglio printing plate are changed in several steps by performing sand blasting as well as wet etching using a mask. This publication says that the depth of depressions having large apertures can be selectively increased while limiting the number of wet etching operations and preventing formation of overhangs, and that the above-described printing failure can be prevented.
Japanese Unexamined Patent Application Publication No. 2007-5445 proposes a method in which different intaglio printing plates are formed respectively for a high-resolution portion and a low-resolution portion, different blankets each having an ink pattern are formed, and a plurality of pattern transfer operations are conducted on one substrate.